MOUTH-PARTS OF THE PAL-EMONID PRAWNS. 53 



It appears, then, tliat tlie flabellum-expodite, wbicli in the 

 iiiijointed limb arises opposite the third and fourth endites, is, 

 when the appendage becomes jointed, generally borne by a double 

 segment, representing those of both the lobes in question, but if, 

 as occasionally happens, the two components of this segment 

 become distinct, the exopodite may be found either upon the 

 proximal of them [Nehalia etc.) or upon the distal (maxillule of 

 Calanus, Notostraca ?). Thus in the axis of the pbyllopod limb 

 the region of the third and fourth endites corresponds to the 

 basipodite of the biramous limb, that of the first two endites to 

 the rest of the protopodite, and all that part which lies beyond 

 the fourth endite to the endopodite. The doubleness of the basi- 

 podite makes necessary certain terms for the distinction of its 

 parts. Its two components may be known as the probasipodite 

 and onetabasipodite, and when either of these alone acts as the 

 basipodite by bearing the exopodite, it is a hemibasipodite. In 

 contradistinction to this the complete double joint may be called 

 the symhasipodite. 



Text-figure 26. Text-figure 27. 



Mandible of I.epas sp. Mandible of Nehalia'^-,. 



For lettering see p. 71. 



In the proximal part of the branchiopod limb, the most per- 

 sistent of the epipodites stands opposite the second endite. The 

 segment to which these structures belong is the coxopodite. If 

 other epipodites (pro-epipodites) be present, they stand in the 

 region of the gnathobase. This region is the so-called " precoxa," 

 or " pleuropodite," which may or may not have originally existed 

 as a free joint in every biramous limb, but has now nearly always 



segment after that which bears the exopodite is here not the ischiopodite, but 

 the second division of the basipodite, or, as it may be called, the meiabasipodite. 

 If this be so, the question arises whether the basipodite be not divided in the 

 Pericarida, whose thoracic endopodites also are flexed between the apparent thn-d 

 and fourth joints. But in that case their apical joint must represent the fused 

 propodite and dactylopodite. With Caiman, I am unable to regard the so-called 

 " stylopodite " as more than an enlarged, terminal spine. If it be one of the primary 

 members of the axis of the limb, it must represent the apical lobe, and the total 

 number of joints in the axis becomes ten, as in the maxilliped of Calanus. 



